U.S. patent number 8,665,850 [Application Number 13/732,172] was granted by the patent office on 2014-03-04 for wireless lan array.
This patent grant is currently assigned to Xirrus, Inc.. The grantee listed for this patent is Michael R. Conley, Michael de la Garrigue, Dirk Ion Gates, Ian Laity, Kurt Sauter, Steve Smith. Invention is credited to Michael R. Conley, Michael de la Garrigue, Dirk Ion Gates, Ian Laity, Kurt Sauter, Steve Smith.
United States Patent |
8,665,850 |
Smith , et al. |
March 4, 2014 |
Wireless LAN array
Abstract
A wireless access device in a local area network (LAN) having a
plurality of transceivers. Each transceiver has a directional
antenna positioned in a substantially circular array to communicate
signals with a plurality of stations in a corresponding sector.
Each sector defines a portion of a coverage area surrounding the
wireless access device. The wireless access device has a network
interface to a data network, and an array controller to control
communication of data between the stations and the transceivers,
and between the transceivers and the network interface. The array
controller is configured to modify channel assignments so as to
minimize channel interference dynamically.
Inventors: |
Smith; Steve (Ventura, CA),
Gates; Dirk Ion (Westlake Village, CA), Laity; Ian (San
Diego, CA), Conley; Michael R. (Thousand Oaks, CA), de la
Garrigue; Michael (Agoura Hills, CA), Sauter; Kurt
(Thousand Oaks, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Smith; Steve
Gates; Dirk Ion
Laity; Ian
Conley; Michael R.
de la Garrigue; Michael
Sauter; Kurt |
Ventura
Westlake Village
San Diego
Thousand Oaks
Agoura Hills
Thousand Oaks |
CA
CA
CA
CA
CA
CA |
US
US
US
US
US
US |
|
|
Assignee: |
Xirrus, Inc. (Thousand Oaks,
CA)
|
Family
ID: |
39886880 |
Appl.
No.: |
13/732,172 |
Filed: |
December 31, 2012 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20130121327 A1 |
May 16, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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13297006 |
Nov 15, 2011 |
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Current U.S.
Class: |
370/338 |
Current CPC
Class: |
H01Q
1/007 (20130101); H04W 80/02 (20130101); H01Q
21/205 (20130101); H01Q 19/106 (20130101); H04W
84/12 (20130101); H01Q 9/285 (20130101); H04W
72/082 (20130101); H04W 80/00 (20130101); H04W
24/08 (20130101); H04W 88/085 (20130101) |
Current International
Class: |
H04W
4/00 (20090101) |
Field of
Search: |
;370/278,334,338
;455/562.1,63.4,101,67.11,450 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nguyen; Phuongchau B
Attorney, Agent or Firm: Rubio-Campos; Francisco A. The
Eclipse Group
Parent Case Text
PRIORITY CLAIM AND CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation application that claims the
benefit of the priority of U.S. patent application Ser. No.
13/297,006, titled "ACCESS POINT IN A WIRELESS LAN ARRAY," by Steve
Smith, Dirk I. Gates, Ian Laity, Michael R. Conley, Michael de la
Garrigue, and Kurt Sauter, filed on Nov. 15, 2011, which is
currently co-pending on the filing date of this application. This
application also claims the benefit of the priority of U.S. patent
application Ser. No. 11/816,003, titled "ACCESS POINT IN A WIRELESS
LAN ARRAY," by Steve Smith, Dirk I. Gates, Ian Laity, Michael R.
Conley, Michael de la Garrigue, and Kurt Sauter, filed on Sep. 22,
2008, which has issued as U.S. Pat. No. 8,160,036. U.S. patent
application Ser. No. 11/816,003 is the parent application of U.S.
patent application Ser. No. 13/297,006.
This application further claims priority of the following
provisional patent applications: 1. Prov. App. Ser. No. 60/660,171,
titled "Wireless LAN Array," by Dirk I. Gates, Ian Laity, Mick
Conley, Mike de la Garrigue, and Steve Smith, filed on Mar. 9,
2005; 2. Prov. App. Ser. No. 60/660,276, titled "Wireless LAN
Array," by Dirk I. Gates, Ian Laity, Mick Conley, Mike de la
Garrigue, and Steve Smith, filed on Mar. 9, 2005; 3. Prov. App.
Ser. No. 60/660,375, titled "Wireless Access Point," by Dirk I.
Gates and Ian Laity, filed on Mar. 9, 2005; 4. Prov. App. Ser. No.
60/660,275, titled "Multi-Sector Access Point Array," by Dirk I.
Gates Ian Laity, Mick Conley, Mike de la Garrigue, and Steve Smith,
filed on Mar. 9, 2005; 5. Prov. App. Ser. No. 60/660,210, titled
"Media Access Controller For Use In A Multi-Sector Access Point
Array," by Mike de la Garrigue and Drew Bertagna filed on Mar. 9,
2005; 6. Prov. App. Ser. No. 60/660,174, titled "Queue Management
Controller For Use In A Multi-Sector Access Point Array," by Mike
de la Garrigue and Drew Bertagna filed on Mar. 9, 2005; 7. Prov.
App. Ser. No. 60/660,394, titled "Wireless LAN Array," by Dirk I.
Gates, Ian Laity, Mick Conley, Mike de la Garrigue, and Steve
Smith, filed on Mar. 9, 2005; 8. Prov. App. Ser. No. 60/660,209,
titled "Wireless LAN Array Architecture," by Dirk I. Gates, Ian
Laity, Mick Conley, Mike de la Garrigue, and Steve Smith, filed on
Mar. 9, 2005; 9. Prov. App. Ser. No. 60/660,393, titled "Antenna
Architecture of a Wireless LAN Array," by Abraham Hartenstein,
filed on Mar. 9, 2005; 10. Prov. App. Ser. No. 60/660,269, titled
"Load Balancing In A Multi-Radio Wireless Lan Array Based On
Aggregate Mean Levels," by Mick Conley filed on Mar. 9, 2005; 11.
Prov. App. Ser. No. 60/660,392, titled "Advanced Adjacent Channel
Sector Management For 802.11 Traffic," by Mick Conley filed on Mar.
9, 2005; 12. Prov. App. Ser. No. 60/660,391, titled "Load Balancing
In A Multi-Radio Wireless Lan Array Based On Aggregate Mean
Levels," by Shaun Clem filed on Mar. 9, 2005; 13. Prov. App. Ser.
No. 60/660,277, titled "System for Transmitting and Receiving
Frames in a Multi-Radio Wireless LAN Array," by Dirk I. Gates and
Mike de la Garrigue, filed on Mar. 9, 2005; 14. Prov. App. Ser. No.
60/660,302, titled "System for Allocating Channels in a Multi-Radio
Wireless LAN Array," by Dirk I. Gates and Kirk Mathews, filed on
Mar. 9, 2005; 15. Prov. App. Ser. No. 60/660,376, titled "System
for Allocating Channels in a Multi-Radio Wireless LAN Array," by
Dirk I. Gates and Kirk Mathews, filed on Mar. 9, 2005; and 16.
Prov. App. Ser. No. 60/660,541, titled "Media Access Controller For
Use In A Multi-Sector Access Point Array," by Dirk I. Gates and
Mike de la Garrigue, filed on Mar. 9, 2005.
This application further claims priority to the following PCT
patent applications: 1. PCT patent application no.
PCT/US2006/008747, titled "Antenna Architecture of a Wireless LAN
Array," 2. PCT patent application no. PCT/US2006/008743, titled
"Wireless LAN Array," filed on Mar. 9, 2006, which claims priority
to the above provisional patent applications; 3. PCT patent
application no. PCT/US2006/008696, titled "Assembly and Mounting
for Multi-Sector Access Point Array," filed on Mar. 9, 2006; 4. PCT
patent application no. PCT/US2006/08698, titled "System for
Allocating Channels in a Multi-Radio Wireless LAN Array," filed
Mar. 9, 2006; and 5. PCT patent application no. PCT/US2006/008744,
titled "Media Access Controller for use in a Multi-Sector Access
Point Array," filed on Mar. 9, 2006.
All of the above-listed US patent applications, US provisional
patent applications, and PCT applications are incorporated by
reference herein.
Claims
What is claimed is:
1. A wireless access device comprising: a plurality of
transceivers, each transceiver having a directional antenna, each
directional antenna positioned in a substantially circular array to
communicate signals with a plurality of stations in a corresponding
sector; a network interface to a data network; and an array
controller in signal communication with each of the plurality of
transceivers, the array controller configured to: assign a
predetermined channel to each of the plurality of transceivers on
which the transceiver communicates with stations in the
corresponding sector, where the predetermined channel is unique
relative to the channels assigned to the other transceivers; modify
the predetermined channel assignment to each of the plurality of
transceivers to dynamically optimize performance; control the
transceivers to generate coverage patterns that provide access to a
border beyond which access is limited, and to generate coverage
patterns that limit reflecting of signals off of an obstacle; and
control communication of data between the stations and the
transceivers, and between the transceivers and the network
interface.
2. A wireless access device according to claim 1 where each of the
plurality of transceivers is a radio that may be configured to
communicate pursuant to the IEEE 802.11a, IEEE 802.11b, IEEE
802.11g or any sub-part of IEEE 802.11.
3. A wireless access device according to claim 2 where the
plurality of transceivers covers all available channels in the band
defined by IEEE 802.11a, IEEE 802.11b, or IEEE 802.11g.
4. A wireless access device according to claim 1 where the array
controller is configured to modify the predetermined channel
assignment pursuant to the standards defined in IEEE 802.11h.
5. A wireless access device according to claim 2 where the
transceivers include a first plurality of transceivers configured
to operate pursuant to IEEE 802.11a and a second plurality of
transceivers configured to operate pursuant to IEEE 802.11b/g.
6. A wireless access device according to claim 5 where each of the
first plurality of transceivers is assigned a unique channel
defined by 802.11a.
7. A wireless access device according to claim 5 where each of the
second plurality of transceivers is assigned a unique
non-overlapping channel defined by 802.11b/g.
8. A wireless access device according to claim 2 where one of the
plurality of transceivers is configured to receive only using an
omni-directional antenna.
9. A wireless access device according to claim 1 where the
plurality of transceivers includes: twelve 802.11a radios
configured to generate a uni-directional sector of at least
30.degree.; three 802.11a/b/g radios configured to generate a
uni-directional sector of at least 120.degree.; and one 802.11a/b/g
radio configured to generate an omni-directional coverage
pattern.
10. A wireless access device according to claim 1 where the
plurality of transceivers includes: four 802.11a radios configured
to generate a uni-directional sector of at least 90.degree.; three
802.11a/b/g radios configured to generate a uni-directional sector
of at least 120.degree.; and one 802.11a/b/g radio configured to
generate an omni-directional coverage pattern.
11. A wireless access device according to claim 1 where the
plurality of transceivers includes: three 802.11a/b/g radios
configured to generate a uni-directional sector of at least
120.degree.; and one 802.11a/b/g radio configured to generate an
omni-directional coverage pattern.
12. A method for providing wireless access to a plurality of
stations comprising: generating a plurality of sectors of coverage
area using a plurality of transceivers, each sector generated using
a directional antenna on a corresponding one of the plurality of
transceivers; assigning a unique predetermined channel to each one
of the plurality of transceivers in a manner that minimizes
adjacent channel interference; communicating signals with at least
one station in at least one of the sectors; managing communication
of signals between the at least one station and a data network by
monitoring performance of each of the plurality of transceivers
communicating with stations; controlling the transceivers to
generate coverage patterns that provide access to a border beyond
which access is limited, and to generate coverage patterns that
limit reflecting of signals off of an obstacle; and modifying the
channel assignment of any of the plurality of transceivers such
that adjacent channel interference is minimized to optimize
performance of the plurality of transceivers.
13. A method according to claim 12 where the step of monitoring
performance of the plurality of transceivers comprises: detecting a
failure of any one of the plurality of transceivers; and
identifying another one of the plurality of transceivers best
capable of replacing the failed one of the plurality of
transceivers.
14. A method according to claim 12 where the step of monitoring
performance of the plurality of transceivers comprises: configuring
at least one of the plurality of transceivers to listen to signals
communicated between any one of the other transceivers and at least
one station; obtaining data from the at least one of the plurality
of transceivers configured to listen; and determining performance
and/or throughput for the plurality of transceivers from the
obtained data.
15. A method according to claim 12 further comprising configuring
each of the plurality of transceivers is a radio configured to
communicate pursuant to the IEEE 802.11a, IEEE 802.11b, or IEEE
802.11g standard.
16. A method according to claim 15 further comprising configuring
the plurality of transceivers to cover all available channels in
the band defined by IEEE 802.11a, IEEE 802.11b, or IEEE
802.11g.
17. A method according to claim 12 further comprising modifying the
channel assignment of the plurality of transceivers according to
standards defined in IEEE 802.11h.
18. A method according to claim 17 further comprising assigning a
unique channel defined by 802.11a.
19. A method according to claim 17 further comprising assigning a
unique non-overlapping channel defined by 802.11b/g.
20. A method according to claim 17 further comprising configuring
one of the plurality of transceivers to receive only using an
omni-directional antenna.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to wireless data communication systems and
more particularly to systems and methods for providing access
points in wireless local area networks.
2. Description of the Related Art
The use of wireless communication devices for data networking is
growing at a rapid pace. Data networks that use "WiFi" ("Wireless
Fidelity") are relatively easy to install, convenient to use, and
supported by the IEEE 802.11 standard. WiFi data networks also
provide performance that makes WiFi a suitable alternative to a
wired data network for many business and home users.
WiFi networks operate by employing wireless access points to
provide users having wireless (or `client`) devices in proximity to
the access point with access to data networks. The wireless access
points contain a radio that operates according to one of three
standards specified in different section of the IEEE 802.11
specification. Radios in access points communicate using
omni-directional antennas in order to communicate signals with
wireless devices from any direction. The access points are then
connected (by hardwired connections) to a data network system that
completes the users' access to the Internet.
The three standards that define the radio configurations are: 1.
IEEE 802.11a, which operates on the 5 GHz band with data rates of
up to 54 Mbps; 2. IEEE 802.11b, which operates on the 2.4 GHz band
with data rates of up to 11 Mbps; and 3. IEEE 802.11g, which
operates on the 2.4 GHz band with data rates of up to 54 Mbps.
The 802.11b and 802.11g standards provide for some degree of
interoperability. Devices that conform to 802.11b may communicate
with 802.11g access points. This interoperability comes at a cost
as access points will incur additional protocol overhead if any
802.11b devices are connected. Devices that conform to 802.11a may
not communicate with either 802.11b or g access points. In
addition, while the 802.11a standard provides for higher overall
performance, 802.11a access points have a more limited range due to
their operation in a higher frequency band.
Each standard defines `channels` that wireless devices, or clients,
use when communicating with an access point. The 802.11b and
802.11g standards each allow for 14 channels. In IEEE Std.
802.11a-1999, 200 channels are defined; each channel centered every
5 MHz from 5000 MHz to 6000 MHz. The 802.11a standard currently
allows for 12 channels in the US. The 14 channels provided by
802.11b and g include only 3 channels that are not overlapping. The
12 channels provided by 802.11a are non-overlapping channels. The
FCC is expected to allocate 11 additional channels in the 5.47 to
5.725 GHz band.
Access points provide service to a limited number of users. Access
points are assigned a channel on which to communicate. Each channel
allows a recommended maximum of 64 clients to communicate with the
access point. In addition, access points must be spaced apart
strategically to reduce the chance of interference, either between
access points tuned to the same channel, or to overlapping
channels. In addition, channels are shared. Only one user may
occupy the channel at any given time. As users are added to a
channel, each user must wait longer for access to the channel
thereby degrading throughput.
As more and more users utilize access points for service, there is
a need to increase the number of clients served by each access
point and to maintain throughput even as the number of clients is
increased.
SUMMARY
Systems consistent with the present invention provide wireless
access devices for providing a plurality of client devices with
wireless access to at least one data network. In one example, the
wireless access devices employ a plurality of transceivers, each
transceiver having a directional antenna. Each directional antenna
is positioned to transmit and receive signals in a sector. Each
sector defines a portion of a coverage area surrounding the
wireless access device. The wireless access device has an array
controller connected to the plurality of transceivers to control
operation of the plurality of transceivers. The wireless access
device also has a network interface to a data network and a media
access controller to control communication of data between the
transceivers and the network interface.
Other systems, methods, features and advantages of the invention
will be or will become apparent to one with skill in the art upon
examination of the following figures and detailed description. It
is intended that all such additional systems, methods, features and
advantages be included within this description, be within the scope
of the invention, and be protected by the accompanying claims.
BRIEF DESCRIPTION OF THE FIGURES
The components in the figures are not necessarily to scale,
emphasis instead being placed upon illustrating the principles of
the invention. In the figures, like reference numerals designate
corresponding parts throughout the different views.
FIG. 1 is a block diagram of a network that uses a wireless access
device.
FIG. 2 is a block diagram of a transceiver module in the wireless
access device in FIG. 1.
FIG. 3 is a block diagram of a controller in the wireless access
device shown in FIG. 1.
FIG. 4 is a diagram illustrating the formation of sectors by the
wireless access device of FIG. 1.
FIGS. 5A-E are diagrams illustrating examples of coverage patterns
formed by an example of the wireless access device of FIG. 1.
FIG. 6A is a diagram of a wireless access device of FIG. 1 labeled
by radio type and number.
FIG. 6B shows coverage patterns formed by the different radio types
on the wireless access device.
FIG. 7 illustrates operation of a wireless access device.
DETAILED DESCRIPTION
FIG. 1 is a block diagram of network 10 that uses a wireless access
device 100 to provide client devices (or "stations"), such as a
laptop computer 20, access to data network services available on
the Internet 160. The wireless access device 100 is connected to a
wired network 120, which may provide a connection to the Internet
160 or other network. Depending on the number of stations and the
size of the area of coverage, the network 10 may include additional
wireless access devices 130. A network management system 120 may be
used to configure and manage the wireless access devices 100,
130.
The wireless access device 100 in FIG. 1 has a substantially
circular structure 108 and includes a array controller 102, a
plurality of transceiver modules 110, and a network interface 114.
The transceiver modules 110 contain one or more transceivers,
radios, for example, and each transceiver is connected to an
antenna 112. The transceiver modules 110 are also connected to the
array controller 102, which operates to configure the transceiver
modules 110 and manage any communications connections involving the
transceivers.
The wireless access device 100 shown in FIG. 1 has sixteen antennas
112. One of ordinary skill in the art will appreciate that any
number of antennas may be used. The antennas 112 that correspond to
the transceivers in the transceiver modules 110 are disposed near
the perimeter of the substantially circular structure 108 of the
wireless access device 100. The antennas 112 are preferably
directional antennas configured to transmit and receive signals
communicated in a radial direction from the center of the wireless
access device 108. Each antenna 112 covers a portion of the
substantially circular area surrounding the wireless access device
100 called a "sector" S.sub.i. The total area covered by all of the
sectors defines a 360.degree. area of coverage of the wireless
access device 100. This means that a station 20 located in a sector
of the area of coverage would be able to communicate wirelessly
with the antenna 112 corresponding with that sector. Multi-sector
coverage is discussed in more detail below with reference to FIGS.
5A-5E.
The network 10 in FIG. 1 implements well-known standards and
protocols used to communicate over the Internet 160. The
transceivers in the wireless access device 100 in FIG. 1
communicate with stations 20 in accordance with the IEEE 802.11
standard (802.11a, 802.11b, 802.11g), which is incorporated herein
by reference. The remainder of this specification describes
operation of examples of the wireless access device 100 in the
context of systems that implement IEEE 802.11a, b, or g. However,
the present invention is not limited to systems that implement any
particular standard. The wireless access device 100 may operate
according to any current or future standard, such as for example,
the forthcoming IEEE 802.11n.
The wireless access device 100 in FIG. 1 has four transceiver
modules 110. Each transceiver module 110 contains four
transceivers, each of which is programmable. In a preferred
configuration, three of the four transceivers (shown in FIG. 1 with
antennas labeled `a`) in each transceiver module 110 are designated
to operate as 802.11a radios. The remaining transceiver (shown in
FIG. 1 with antenna labeled `abg`) may be programmed to operate
according to any of 802.11a, b, or g. Each transceiver is
configured to operate on an assigned channel. The channel may be
one of the twelve channels available using the 802.11a standard or
one of the fourteen channels available using the 802.11b/g
standard.
The wireless access device 100 communicates with stations 20
wirelessly. The stations 20 may be any device enabled to
communicate wirelessly with the wireless access device 100 such as,
without limitation, laptop computers, mobile telephones (for
voice-over-LAN, or VOWLAN applications), personal digital
assistants, handheld computers, etc. In examples described here,
the stations are enabled to operate in accordance with one or more
of the 802.11 standards. When the station 20 enters the coverage
area of the wireless access device 100, it may send a request to
connect to the access point 160. The wireless access device 100 may
perform an authentication process in a login session. Once
authenticated, the user of the station 20 may be connected to the
Internet 160.
FIG. 2 is a block diagram of a transceiver module 210 that may be
implemented in the wireless access device 100 shown in FIG. 1. The
transceiver module 210 includes four radios, one of which is an
`abg` radio 220 and three of which are `a` radios 222. All four
radios 220, 222 include an amplifier 230, a radio signal processor
240, and a baseband processor 250. The four radios 220, 222
communicate with a transceiver module interface 260, which allows
the transceiver module 210 to communicate with the rest of the
wireless access device. One of ordinary skill in the art will
appreciate that four radios 220, 222 are shown as an example. The
transceiver module 210 may also have one, two, or any number of
radios.
Each radio 220, 222 connects to an antenna 212, which transmits and
receives radio signals received from the amplifier 230. As
described with reference to FIG. 1, the antennas 212 are
directional antennas, which concentrate signal power in one
direction. Directional antennas can therefore cover greater
distances than omni-directional antennas used in typical wireless
access devices. The multiple radios with radially disposed
directional antennas advantageously provides a 360.degree. coverage
pattern that is larger than that of radios with omni-directional
antennas used in current access points.
The baseband processor 250 processes the digital data that is
either being received or transmitted by the radio 220, 222. The
baseband processor 250 implements protocols required for such
functions as assembling/disassembling payloads. The baseband
processor 250 performs the digital functions required to implement
the 802.11 standard. Preferably, the baseband processor 250 is
programmable and may be configured for any of the three standards
(802.11a, 802.11b, 802.11g). One example of a baseband processor
250 that may be implemented is the Agere WL64040.
The radio signal processor 240 modulates signals to be transmitted
and demodulates signals that have been received. The radio signal
processor 240 is preferably programmable to implement either the
modulation schemes specified by 802.11b/g or 802.11a. One example
of a radio signal processor 240 that may be implemented is the
Agere WL54040.
The amplifier 230 generates the radio signal to be transmitted by
the transceiver 220, 222 and amplifies signals being received by
the antenna 212. One example of an amplifier that may be
implemented in the transceiver module 210 is the SiGe Semiconductor
SE2535L for the 5 GHz or 802.11a radios, and the SiGe Semiconductor
SE2525L for the 2.4 GHz or 802.11b/g radios.
In the transceiver module in FIG. 2, the amplifier 230, radio
signal processor 240, and/or baseband processor 250 may be
programmable so that the array controller 102 (in FIG. 1) may
control the transceiver module 200 in a manner that provides
certain features. For example, the array controller 102 (in FIG. 1)
may control the amplifiers 230 in a manner that makes the coverage
pattern of the wireless access device 102 larger or smaller
depending on the needs of the implementation. In addition, the
baseband processor 250 may communicate information (such as signal
strength) about the radio connection between the wireless access
device 100 and the stations 20.
It is noted that the following description refers to transceivers
as radios. Those of ordinary skill in the art will appreciate that
the term "radio" is not intended as limiting the transceiver to any
particular type.
FIG. 3 is a block diagram of an array controller 300 that may be
implemented in the wireless access device 100 shown in FIG. 1. The
array controller 300 includes a processor 310, a packet and queue
controller 320, a medium access controller 330, a radio interface
340, and a data network interface 350.
The processor 310 provides computing resources to the wireless
access device. The processor 310 may be any suitable custom or
commercial microprocessor, microcontroller, computing chip or other
type of processor. The array controller 300 also includes
supporting circuitry for the processor 310 such as clock circuitry,
I/O ports, memory (including Read Only Memory, or ROM, Random
Access Memory, or RAM, Flash memory, Programmable Rom or PROM,
etc.), direct memory access, etc. The processor 310 may also manage
a bus system for communicating with its support circuitry and with
the packet and queue controller 320, data network interface 350 and
medium access controller 330. In one example, the processor 310 is
a Motorola 8540 800 MHz CPU supported by 64 MB expandable system
FLASH memory, 128 MB DDR 333 expandable system RAM, and a serial
interface (RS232-RJ45 connector). An optional security co-processor
may also be included.
The data network interface 350 includes input/output circuitry for
communicating over a data network. The array controller 300
implements standards and protocols that allow for communication
over the Internet. The data network interface 350 preferably allows
for the highest possible speed connection. In one example, the data
network interface 350 includes primary and secondary Gigabit
Ethernet interfaces, a Fast Ethernet interface, and failover
support between the Gigabit Ethernet interfaces.
The packet and queue controller 320 handles receiver and
transmitter queues, performs DMA functions, resolves fragmentation,
and performs packet translation. The medium access controller 330
provides all IEEE 802.11 MAC services for transceivers. For the
wireless access device 100 in FIG. 1, the medium access controller
330 provides 802.11 MAC services for as many as sixteen
transceivers. Both the packet and queue controller 320 and the
medium access controller 330 are preferably implemented as
application specific integrated circuits (ASIC).
The array controller 300 performs the programmed functions that
control the wireless access device 100 as an access point.
Functions and features of the operations that the array controller
300 performs include: 1. General implementation IEEE 802.11 Access
Point functionality. 2. Non-blocking packet processing from/to any
radio interface. In typical wireless access devices that employ a
single, omni-directional radio, a packet that is being transmitted
may block other packets from access to the medium. This may occur
in either direction. Stations typically transmit packets to an
access point when the medium is not busy. If the medium is busy
with packets from other stations, for example, the packet is
blocked. Similarly, the access point may be attempting to send a
packet to a station. If other packets are being sent to another
station, the original packet is blocked from access to the medium.
In the wireless access device 100, when a station is blocked from
communicating a packet to one radio, it may switch to another radio
that is not blocked. If the wireless access device 100 is blocked
from sending a packet via one radio, it may switch to another
radio. 3. Dynamic automatic channel assignment. The array
controller 300 implements algorithms and/or other schemes for
assigning channels of the 802.11 standards to the multiple radios.
Channels are allocated to radios in a manner that reduces adjacent
channel interference (ACI). 4. Directional awareness of where a
wireless station is in geographic relationship to the wireless
access device 100. The array controller 300 receives information
such as signal strength, and for each station, may keep track of
how the signal strength changes over time. In addition, even if one
radio is locked in and "connected" to a station, another radio may
receive signals and thus, "listen" to the station. The signal
strength in relation to the specific radios gathering signal
information provide the array controller with sufficient
information to create a directional awareness of the location of
the wireless station. 5. Station mobility services whereby a
station can instantly roam from one sector to another without
requiring re-authentication of the station. As a wireless station
moves in the coverage area space of the wireless access device, the
signal strength sensed by the array controller changes. As the
signal strength of the station becomes weaker, the radio associated
with the adjacent sector locks in and "connects" with the station
without requiring re-authentication. 6. Wireless quality of
service. 7. Enhanced load balancing of wireless stations. 8.
Constant RF monitoring of channel conditions and security threats
9. Wireless Security processing 10. Internal Authentication Server.
Typically, authentication takes place at a server or router that is
wired to the access points. In the wireless access device 100,
authentication may be done by the array controller 300. 11. Wired
Networking protocol support. 12. System failover handling and error
handling. Because sectors overlap, when a radio fails, the adjacent
radios may lock in with stations being handled by the failed radio.
In some examples of the wireless access device 100, the array
controller 300 may increase power to adjacent sectors to ensure
coverage in any area covered by the failed sector. In addition,
when multiple access devices are deployed, one wireless access
device may increase power and expand a sector to cover area left
without service when a radio fails in an adjacent wireless access
device. 13. System management functions.
As discussed above, examples of wireless access devices and systems
that employ wireless access devices described in this specification
(without limitation) operate in the wireless LAN environment
established by the IEEE 802.11 standardization body. The IEEE
802.11 standards including (without limitation): 1. IEEE 802.11,
1999 Edition (ISO/IEC 8802-11: 1999) IEEE Standards for Information
Technology--Telecommunications and Information Exchange between
Systems--Local and Metropolitan Area Network--Specific
Requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) Specifications. 2. IEEE 802.11a-1999 (8802-11:
1999/Amd 1: 2000(E)), IEEE Standard for Information
technology--Telecommunications and information exchange between
systems--Local and metropolitan area networks--Specific
requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) specifications--Amendment 1: High-speed
Physical Layer in the 5 GHz band. 3. IEEE 802.11b-1999 Supplement
to 802.11-1999, Wireless LAN MAC and PHY specifications: Higher
speed Physical Layer (PHY) extension in the 2.4 GHz band. 4.
802.11b-1999/Cor1-2001, IEEE Standard for Information
technology--Telecommunications and information exchange between
systems--Local and metropolitan area networks--Specific
requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) specifications--Amendment 2: Higher-speed
Physical Layer (PHY) extension in the 2.4 GHz band--Corrigendum1.
5. IEEE 802.11d-2001, Amendment to IEEE 802.11-1999, (ISO/IEC
8802-11) Information technology--Telecommunications and information
exchange between systems--Local and metropolitan area
networks--Specific requirements--Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY) Specifications:
Specification for Operation in Additional Regulatory Domains. 6.
IEEE 802.11F-2003 IEEE Recommended Practice for Multi-Vendor Access
Point Interoperability via an Inter-Access Point Protocol Across
Distribution Systems Supporting IEEE 802.11 Operation. 7. IEEE
802.11g-2003 IEEE Standard for Information
technology--Telecommunications and information exchange between
systems--Local and metropolitan area networks--Specific
requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) specifications--Amendment 4: Further
Higher-Speed Physical Layer Extension in the 2.4 GHz Band. 8. IEEE
802.11h-2003 IEEE Standard for Information
technology--Telecommunications and Information Exchange Between
Systems--LAN/MAN Specific Requirements--Part 11: Wireless LAN
Medium Access Control (MAC) and Physical Layer (PHY)
Specifications: Spectrum and Transmit Power Management Extensions
in the 5 GHz band in Europe. 9. IEEE 802.11i-2004 Amendment to IEEE
Std 802.11, 1999 Edition (Reaff 2003). IEEE Standard for
Information technology--Telecommunications and information exchange
between system--Local and metropolitan area networks Specific
requirements--Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) specifications--Amendment 6: Medium Access
Control (MAC) Security Enhancements. 10. IEEE 802.11j-2004 IEEE
Standard for Information technology--Telecommunications and
information exchange between systems--Local and metropolitan area
networks--Specific requirements--Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY)
specifications--Amendment 7: 4.9 GHz-5 GHz Operation in Japan. All
of the above-listed standards are incorporated herein by
reference.
Radios operating under 802.11 may operate in one of two frequency
bands: the 2.4 GHz band and the 5 GHz band. The IEEE specifies
multiple channels within each band (see Table 1). Channels are
defined as allocations of frequency spectrum with specified center
frequencies and spacing. For example, in the 2.4 GHz band there are
14 defined channels starting at a center frequency of 2.412 GHz and
incrementing up to 2.484 GHz at 5 MHz intervals. Channels are
considered overlapping if their bands overlap above a certain power
threshold. For instance, in the 2.4 GHz region each channel
operates with a frequency band of 12 MHz on either side of the
center frequency. So with 14 channels defined with center
frequencies 5 MHz apart, several of them are overlapping. In fact,
there are only three channels (channels 1, 6, and 11) that do not
overlap in the 2.4 GHz band. Their center frequencies are 2.412
GHz, 2.437 GHz and 2.462 GHz.).
In the 5 GHz band, the IEEE Std. 802.11a-1999 defines 200 channels;
each channel centered every 5 MHz from 5000 MHz to 6000 MHz. The
802.11a standard currently allows for 12 channels in the US. The 12
channels provided by 802.11a are non-overlapping channels. The FCC
is expected to allocate 11 additional channels in the 5.47 to 5.725
GHz band. Those of ordinary skill in the art will appreciate that
the channels described herein are for purposes of illustrating an
example and not intended as any limitation on the scope of the
invention. Embodiments of the present invention that are designed
to implement any part of the 802.11 standard may use any set of
channels specified by any part of the IEEE 802.11 standard whether
such channels are available now or in the future.
TABLE-US-00001 TABLE 1 IEEE 802.11 U.S. Radio Channel Assignments
IEEE 802.11 A IEEE 802.11 B/G (5.0 GHz Band) (2.4 GHz Band) Channel
Frequency Channel Frequency Number (MHz) Number (MHz) 36 5180 1
2412 40 5200 2 2417 44 5220 3 2422 48 5240 4 2427 52 5260 5 2432 56
5280 6 2437 60 5300 7 2442 64 5320 8 2447 149 5745 9 2452 153 5765
10 2457 157 5785 11 2462 161 5805 12 2467 13 2472 14 2484
The wireless access device 100 in FIG. 1 assigns channels to the
sixteen radios in a manner that enhances performance, throughput,
coverage area and capacity. Typical access points use one radio
with a coverage area defined by an omni-directional antenna and
assigned to a single channel. Therefore, all of the users in the
coverage area tune in to the same channel in order to communicate
with the access point. In the wireless access device 100 in FIG. 1,
each radio forms a different sector defining a portion of a
substantially circularly-defined coverage pattern. In addition,
each radio is assigned a unique channel so that no two radios in
one device communicate over the same channel.
FIG. 4 is a diagram illustrating the formation of sectors by the
wireless access device of FIG. 1. The wireless access device 100
has 16 radios 412 divided into groups of four radios 412 mounted on
each of four transceiver modules 410. An array controller 402 is
located roughly in the center of the wireless access device 100
where it connects with each of the four transceiver modules 410 at
inter-module connections 408. The inter-module connections 408
contain communication paths (via a bus or set of signal paths on a
connector) that implement the interface between the array
controller 402 and the radios 412. One of ordinary skill in the art
will appreciate that the wireless access device 100 may have more
or fewer than 16 radios. For example, in other embodiments, the
wireless access device 100 has 4 radios (e.g. three `abg`
uni-directional radios and one `abg` omni-directional) or 8 radios
(e.g. four `a` unidirectional radios, three `abg` unidirectional
radios, one `abg` omni-directional radio) or even 24 radios
(anywhere from 16-24 `a` radios and 0-8 `abg` radios). The number
of radios is not important so long as multiple radios may be
configured to provide a 360.degree. coverage area.
As discussed, each radio 412 contains a directional antenna
configured to establish a coverage area in a sector 450 that
radiates out from the wireless access device 100. The radios 412
may be individually controlled such that when they are all
operating they may form a coverage pattern that surrounds the
wireless access device 100. The coverage pattern created by the
wireless access device 100 may be similar to coverage patterns
created by existing access points that use one radio radiating out
of an omni-directional antenna. However, the wireless access device
100 in FIG. 4 uses sixteen radios 412 radiating out of more
powerful directional antennas to create a coverage pattern area
that is significantly greater than that of a typical access point.
In addition, the sectors 450 created by the radios 412 in the
wireless access device 100 advantageously overlap to provide
features not currently available in typical access points. The
radios 412 are also programmable such that they may be controlled
to operate at power levels that allow for coverage patterns that
are suited to the layout of the implementation. Examples are
discussed below with reference to FIGS. 5A-E.
In FIG. 5A, a wireless access device 100 is implemented in an
implementation I with all of the radios in the wireless access
device 100 configured to communicate with stations within a
coverage area 502. The radios in the wireless access device 100
form sectors. A first sector 530 is shown with an adjacent sector
540 along with an area of overlap 550 formed by the overlap of the
first and second sectors 530, 540. FIG. 5A illustrates one of many
advantages that the wireless access device 100 has over typical
access points. The wireless access device 100 includes programmable
and configurable control over the operation of the radios on the
wireless access device 100. When deployed, the wireless access
devices 100 may be configured to create a coverage pattern that is
suitable for by the exact implementation I. For example, in FIG.
5A, the coverage pattern 502 has been configured to conform to the
implementation I. The wireless access device 100 may be configured
such that the radios that create a set of coverage patterns 522,
524, 526, 528, 530 that project towards a side 580 communicate
signals at a lower power limiting the extent of the coverage area
created by each radio. This is illustrated by a set of middle
sectors 524, 526, 528 covering less distance than outer sectors
522, 530, which cover the corners or the implementation I along the
side 580. This implementation I advantageously substantially limits
the ability for a station to connect from beyond the wall along the
side 580 of implementation I.
FIG. 5B illustrates how the wireless access device 100 may be
configured to provide special features in a specific
implementation. In FIG. 5B, the wireless access device 100 is
implemented in a space 570 in which the resident desires to have
wireless Internet access. The space 570 is located with one side
590, which faces an open and public area from which hackers or
otherwise unauthorized users may attempt to gain access to the
Internet via the wireless access device 100. The wireless access
device 100 may be used to provide users in the space 570 with
access to the Internet while limiting access by those on the other
side of 590. One way as illustrated in FIG. 5B is to place the
wireless access device 100 along the side 590 and turn off radios
that would create sectors on the other side of 590, and turn on the
radios that create sectors in the space 570. Such an implementation
would yield a coverage pattern similar to the one shown in FIG.
5B.
FIG. 5C shows how the wireless access device 100 may be configured
to limit the affects of obstacles that may cause reflections in the
radio signals. Reflections in typical access points may cause
multi-path interference. When radio signals reflect off of
obstacles, the reflections may reach the station as different
signals coming from different directions, or multiple paths. The
wireless access device 100 may be configured to avoid multi-path
interference by configuring the radios to avoid generating sectors
that could reach the obstacle. In FIG. 5C, the wireless access
device 100 is shown generating sectors 520, 540, but not generating
any sectors in the direction of obstacle 575.
FIG. 5D illustrates how overlapping sectors may be used to provide
radio frequency failover so that stations do not lose connectivity
when a radio fails, or is otherwise unavailable. In FIG. 5D,
wireless access device 100 has three radios creating a sector each
(R1, R2, R3). In FIG. 5E, the wireless access device 100 has lost
the radio associated with sector R2. However, sectors R1, R2, R3
advantageously overlap. The wireless access device 100 may switch
stations in sector R2 that were connected via the radio that
generated sector R2 to the radios that created either of sectors R1
or R3.
FIG. 6A is a diagram of a wireless access device 100 of FIG. 1
labeled by radio type and number. Radios that communicate, or are
configured to communicate, as 802.11a radios only are labeled `a.`
Radios that may be programmed or configured to communicate using
802.11a, b, or g radios are labeled `abg.` The twelve `a` radios
610 (a1-a12) are assigned a unique one of the twenty-three channels
available under the 802.11a standard. Three of the four `abg`
radios are assigned the three non-overlapping channels available
under the 802.11b/g standards. The fourth `abg` radio is
implemented as an omni-directional radio in listen mode
exclusively.
FIG. 6B shows coverage patterns formed by the different radio types
on the wireless access device. The twelve `a` radios 610 each have
a coverage area emanating in a sector that spreads out more than
30.degree.. The sectors of the twelve `a` radios 610 may combine to
form a substantially circular 802.11a coverage pattern 620.
Preferably, the sectors are larger than 30.degree. in order to
create overlap between the sectors, such as for example, the
overlap 650 between sectors 630 and 640. FIG. 6B also shows the
three `abg` radios 611 with the coverage area of more than
120.degree.. The sectors combine to provide a 360.degree. coverage
pattern. However, each sector is more than 120.degree. to create
overlap between the sectors. The fourth `abg` radio 613 is
configured as an omni-directional radio able to communicate in all
directions. The fourth `abg` radio 613 is used as a monitor or a
sniffer radio in a listen-only mode. This radio listens to each
channel in sequence to build a table of all stations and access
devices. This table may be compared to an administrator controlled
list of allowed stations and access devices. Stations and access
devices not in the administrator controlled list are termed rogues.
One function performed by the fourth `abg` radio 613 is to detect
unauthorized stations in the coverage area.
FIG. 7 is a diagram of a wireless access device 700 connected
wirelessly to a plurality of stations 720a-o via channels allocated
to the plurality of radios a1-a12, afg1-afg4 on the wireless access
device 700. The radios are labeled according to their type and
radio numbers. Inside the circles representing the radios are
numbers identifying the channels assigned to the radio. As shown,
radios a1-a12 and afg1-afg4 are assigned channels as shown in Table
2 below:
TABLE-US-00002 TABLE 2 Radio No. Channel Frequency (MHz) A9 36 5180
A12 40 5200 A3 44 5220 A6 48 5240 A10 52 5260 A1 56 5280 A4 60 5300
A7 64 5320 A11 149 5745 A2 153 5765 A5 157 5785 A8 161 5805 M --
Monitor radio that can listen on any abg channel abg1 1 2412 abg3 6
2437 abg4 11 2462
The radios in the wireless access device 700 are advantageously
assigned different channels. The radios in FIG. 7 and the array
controller (described above with reference to FIG. 3) are housed
within a single enclosure tightly coupled by digital bus. The
housing provides a central control point for the sixteen radios
that is not tethered by any cabled bus.
The stations 720a-o in FIG. 7 represents stations attempting to
connect to the wireless access device 700. The arrows indicate the
stations' ability to connect to a particular radio as well as the
ability of the station to communicate using the appropriate
protocol (i.e. 802.11a, b, or g). To illustrate, station 720a is a
target wireless client attaching to the wireless access device 700
using protocols specified by 802.11a. Radios a5, a6, and a7
generate sectors that preferably overlap such that station 720a may
connect to either one of the three radios. Each radio is assigned a
unique channel that does not overlap with any other channel.
If the radio to which station 720a is connected fails, or is
otherwise unable to provide service to station 720a, the array
controller is able to switch the connection to station 720a over to
one of the adjacent radios. The IEEE 802.11a, b, and g protocols
permit radios to "listen" to signals being communicated with
stations that are connected to another radio. The array controller
may obtain data such as signal strength and directional awareness
and other factors that allow it to determine which radio is best
suited to continue communicating with the station 720a. The array
controller may use data obtained from "listening" radios to
determine performance, throughput, or other performance factors.
The array controller 300 may compile the data for all of the radios
and use the data to determine whether a different radio should be
used, and if necessary to re-assign or modify the channel
assignment of the radio. The array controller 300 may also perform
a modification of the channel assignments of other radios in order
to minimize ACI. The array controller 300 may change the channel
assignments if a radio fails, or if the array controller 300
determines that better performance may be achieved by modifying the
channel assignments, for example to enhance load balancing.
The wireless access device 700 is connected to a Gigabit Ethernet
port 780, which provides a direct connection to the user's
network.
Although the controller 300 depicted in FIG. 3 uses memory, one
skilled in the art will appreciate that a substantial part of
systems and methods consistent with the present invention may be
stored on or read from other machine-readable media, for example,
secondary storage devices such as hard disks, floppy disks, and
CD-ROMs; a signal received from a network; or other forms of ROM or
RAM either currently known or later developed. Further, although
specific components of wireless access device 100 are described,
one skilled in the art will appreciate that a network access device
suitable for use with methods, systems, and articles of manufacture
consistent with the present invention may contain additional or
different components.
The foregoing description of an implementation has been presented
for purposes of illustration and description. It is not exhaustive
and does not limit the claimed inventions to the precise form
disclosed. Modifications and variations are possible in light of
the above description or may be acquired from practicing the
invention. For example, the described implementation includes
software but the invention may be implemented as a combination of
hardware and software or in hardware alone. Note also that the
implementation may vary between systems. The claims and their
equivalents define the scope of the invention.
* * * * *